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1.
Occurrence number of red tides in Osaka Bay in Japan is more than 20 cases every year. Diatom red tide was dominant in Osaka Bay, but the non-diatom red tide was dominant in early 1990s. Therefore, the material cycling in Yodo River estuary in Osaka Bay during August from 1991 to 2000 was analyzed by using the numerical ecosystem model and field observation data to clarify the reasons of change in red tide species. Year-to-year variation in calculated concentration ratio of diatom to non-diatom corresponds to the variation in observed ratio of red tide days of diatom to non-diatom. Limiting nutrient of primary production is phosphate over the period. Diatom dominated from 1991 to 1993, but it was difficult for non-diatom to grow due to the limitation by physical condition. Non-diatom was able to grow because of good physical and nutrient conditions from 1994 to 1996. And diatom dominated again under the good physical condition, and phosphorus supply was not enough for non-diatom to grow from 1998 to 2000. Phosphate concentration in the lower layer of Yodo River estuary was important to the variation in red tide species in the upper layer of Yodo River estuary. 相似文献
2.
《Journal of Geodynamics》2006,41(4-5):487-493
The focus of this paper is to present the concepts for a new dynamic, i.e. database-driven information system for the International Earth Rotation and Reference Systems Service (IERS). Its goal is to coordinate the data and information flow between the participating institutions. Therefore, all relevant data and products of the IERS should be archived to guarantee their long-term availability. At the same time the consistency and timeliness of the contents of the information system can be guaranteed by managing the information in a database. Additionally, the metadata of all products (including the IERS publications) should be modelled in a database to allow the users to search for specific data or topics with respect to space, time and content. In order to be able to link related data the heterogeneous formats of the products have to be transformed into a common format. The eXtensible Markup Language (XML) is going to be used, to perform this ambitious task. The usage of XML not only allows to link related data but also to easily exchange data and to present them in different ways like Web pages, pdf, etc. The system will be completed by several tools to manage and coordinate the tasks of the Central Bureau (CB) and by an information system with respect to IERS-related topics. The standardised database tools will also allow an easy exchange of information with and links to other databases within the IGGOS project to realize a powerful instrument to serve the Earth observing system. 相似文献
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4.
D. Shimozuru 《Bulletin of Volcanology》1968,32(2):383-394
Energy of volcanic eruption is divided into various ways, such as lava flows, ash production, explosion, ground vibration, air waves and so on. In order to elucidate the cruptive mechanism, energy partition of volcanic eruption in unit time is considered to be a key to solve the problem. In this short paper, partition of eruption energy was calculated for typical three basaltic volcanoes. Ratio of tremor energy to thermal energy is almost the same for both Mihara and Nyragongo in spite of their different eruptive mechanism. Tremor energy was found to be small for Kilauea Volcano compared with the above two volcanoes. This was attributed to the different source mechanism of tremor. Partition of eruption energy was calculated for Also Volcano which showed phreatic explosion in 1958. Kinetic energy is almost ten times of thermal energy. Ratio of energy converted to elastic waves to thermal energy is found to be equivalent to the ratio of energy of elastic waves to the chemical energy in case of explosion of chemical explosives. 相似文献
5.
The deflection, at a step-shelf fronted coast, of a constant potential vorticity current in a reduced-gravity, inviscid model ocean is studied theoretically. The step shelf, with a depth smaller than the reservoir depth, forces the uplifting of the approaching current and causes water column foreshortening, leading to relative vorticity generation that enhances current deflection to the right (facing the coast). As a consequence, in comparison to the case of a vertical wall coast, the proportion of the transport to the right is increased. For normal incidence for a shelf-depth/reservoir-depth ratio of 0.3 and shelf width to deformation radius ratio of 1.5, more than 90% of the approaching current transport goes to the right and less than 10% to the left. In addition, the (barotropic) dynamic pressure at the coast is low to the right and high to the left (with the highest pressure at the stagnation point). In the vertical wall case, the wall pressures on the flank are equal. For oblique incidence from the left, the deflection to the left is drastically reduced. In fact, there is practically no steady-state flow diverted to the left (less than 2%) when the approach angle is greater than 60° to the left of normal. In the vertical wall case, the same angle would have to be 90° for the flow to the left to vanish, namely only when the approach current is parallel to the coast to the right. 相似文献
6.
Water introduced to surface drainages, such as agricultural and roadway runoff, mine drainage, or coalbed natural gas (CBNG)-produced water, potentially can be of environmental concern. In order to mitigate potential environmental effects, it may be important to be able to trace water discharged to the surface as it infiltrates and interacts with near-surface aquifers. We have chosen to study water withdrawn during CBNG production for isotope tracing in the hyporheic zone because it poses a variety of economic, environmental, and policy issues in the Rocky Mountain states. Ground water quality must be protected as CBNG water is added to semiarid ecosystems. Strontium (Sr) isotopes are effective fingerprints of the aquifer from which water originates. In this study, CBNG water was found to have a higher (87)Sr/(86)Sr ratio than the local alluvial aquifer water. This measurable difference allows the strontium isotope ratio and concentration to be used as tracers of CBNG water following its discharge to the surface. The dissolution and mobilization of salts from soil are an important contributor to ground water quality degradation. In the Powder River basin of Wyoming, the soils are calcium carbonate-buffered systems. The chemical similarity of strontium to calcium allows it to substitute into calcium minerals and enabled us to use strontium isotopes to identify calcium salts mobilized from the soil. Strontium isotopes are an effective monitor of the source of ions and the volume and direction of introduced water flow in the hyporheic zone. 相似文献
7.
Anton Ziolkowski 《Geophysical Prospecting》2010,58(1):41-54
The goal of vibroseis data acquisition and processing is to produce seismic reflection data with a known spatially-invariant wavelet, preferably zero phase, such that any variations in the data can be attributed to variations in geology. In current practice the vibrator control system is designed to make the estimated groundforce equal to the sweep and the resulting particle velocity data are cross-correlated with the sweep. Since the downgoing far-field particle velocity signal is proportional to the time-derivative of the groundforce, it makes more sense to cross-correlate with the time-derivative of the sweep. It also follows that the ideal amplitude spectrum of the groundforce should be inversely proportional to frequency. Because of non-linearities in the vibrator, bending of the baseplate and variable coupling of the baseplate to the ground, the true groundforce is not equal to the pre-determined sweep and varies not only from vibrator point to vibrator point but also from sweep to sweep at each vibrator point. To achieve the goal of a spatially-invariant wavelet, these variations should be removed by signature deconvolution, converting the wavelet to a much shorter zero-phase wavelet but with the same bandwidth and signal-to-noise ratio as the original data. This can be done only if the true groundforce is known. The principle may be applied to an array of vibrators by employing pulse coding techniques and separating responses to individual vibrators in the frequency domain. Various approaches to improve the estimate of the true groundforce have been proposed or are under development; current methods are at best approximate. 相似文献
8.
黄河水资源贫乏,水污染严重,水资源供需矛盾日益尖锐,黄河流域水资源保护面临着诸多的困难和压力.新《水法》的颁布,给黄河水资源保护带来新的机遇和挑战,依法建立法制化、社会化的流域与区域相结合的水资源保护管理体系,完善法规,建立健全执法体系,以水功能区划管理为重心,实施入河总量控制,建立和完善重大水污染事件快速反应机制,加强水质监测机制与技术创新,加强水资源保护前期和科研工作,建设水资源保护信息管理系统,采取多部门联合治污等项措施,是做好黄河流域水资源保护工作的重要前提和任务. 相似文献
9.
Restricted parts of the Valley of Mexico have been plagued by swarms of small earthquakes during recent years. The cause of these events is puzzling, but they may relate to massive artificial changes in the hydrology of the lake-bed which underlies most of Mexico City. If the valley responds elastically, plane strain finite element calculations can be used to relate geologic and seismic structure to observed seismicity and overall stability of the valley. These calculations show that unstable zones and areas of local seismicity coincide if the triggering mechanism of the seismicity is related to variations of pore pressure and water load.In order to make such a connection it is necessary to ascribe the generating mechanism of the seismicity to the density and elastic modulus anomalies associated with the valley structure, and to suggest that the phenomenon that triggers this seismicity is related to changes in water content of the near surface formations. 相似文献
10.
The dynamic response of tall civil structures due to earthquakes is very important to civil engineers. Structures exposed to earthquakes experience vibrations that are detrimental to their structural components. Structural pounding is an additional problem that occurs when buildings experience earthquake excitation. This phenomena occurs when adjacent structures collide from their out‐of‐phase vibrations. Many energy dissipation devices are presently being used to reduce the system response. Tuned mass dampers (TMD) are commonly used to improve the response of structures. The stiffness and damping properties of the TMD are designed to be a function of the natural frequency of the building to which it is connected. This research involves attaching adjacent structures with a shared tuned mass damper (STMD) to reduce both the structures vibration and probability of pounding. Because the STMD is connected to both buildings, the problem of tuning the STMD stiffness and damping parameters becomes an issue. A design procedure utilizing a performance function is used to obtain the STMD parameters to result in the best overall system response. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
11.
Quantifying distributional behavior of extreme events is crucial in hydrologic designs. Intensity Duration Frequency (IDF) relationships are used extensively in engineering especially in urban hydrology, to obtain return level of extreme rainfall event for a specified return period and duration. Major sources of uncertainty in the IDF relationships are due to insufficient quantity and quality of data leading to parameter uncertainty due to the distribution fitted to the data and uncertainty as a result of using multiple GCMs. It is important to study these uncertainties and propagate them to future for accurate assessment of return levels for future. The objective of this study is to quantify the uncertainties arising from parameters of the distribution fitted to data and the multiple GCM models using Bayesian approach. Posterior distribution of parameters is obtained from Bayes rule and the parameters are transformed to obtain return levels for a specified return period. Markov Chain Monte Carlo (MCMC) method using Metropolis Hastings algorithm is used to obtain the posterior distribution of parameters. Twenty six CMIP5 GCMs along with four RCP scenarios are considered for studying the effects of climate change and to obtain projected IDF relationships for the case study of Bangalore city in India. GCM uncertainty due to the use of multiple GCMs is treated using Reliability Ensemble Averaging (REA) technique along with the parameter uncertainty. Scale invariance theory is employed for obtaining short duration return levels from daily data. It is observed that the uncertainty in short duration rainfall return levels is high when compared to the longer durations. Further it is observed that parameter uncertainty is large compared to the model uncertainty. 相似文献
12.
byK. L. Ricciardi 《Ground water》2009,47(5):675-685
Optimal cost pump-and-treat ground water remediation designs for containment of a contaminated aquifer are often developed using deterministic ground water models to predict ground water flow. Uncertainty in hydraulic conductivity fields used in these models results in remediation designs that are unreliable. The degree to which uncertainty contributes to the reliability of remediation designs as measured by the characterization of the uncertainty is shown to differ depending upon the geologic environments of the models. This conclusion is drawn from the optimal design costs for multiple deterministic models generated to represent the uncertainty of four distinct models with different geologic environments. A multi scenario approach that includes uncertainty into the remediation design called the deterministic method for optimization subject to uncertainty (DMOU) is applied to these distinct models. It is found that the DMOU is a method for determining a remediation design subject to uncertainty that requires minimal postprocessing efforts. Preprocessing, however, is required for the application of the DMOU to unique problems. In the ground water remediation design problems, the orientation of geologic facies with respect to the orientation of flow patterns, pumping well locations, and constraint locations are shown to affect the preprocessing, the solutions to the DMOU problems, and the computational efficiency of the DMOU approach. The results of the DMOU are compared to the results of a statistical analysis of the effects of the uncertainty on remediation designs. This comparison validates the efficacy of the DMOU and illustrates the computational advantages to using the DMOU over statistical measures. 相似文献
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14.
J. B. Berrill 《地震工程与结构动力学》1983,11(3):427-436
This paper examines the risk from fault offset to a building constructed over the surface trace of a fault. An expression relating the magnitude of surface offset to its return period is derived using classical seismic hazard analysis. The risk from fault offset is compared with that due to ground shaking by comparing offsets and MM intensities with equal likelihoods of occurrence. The comparison of risks is useful since it enables risk from fault movement to be related to levels of community acceptance as expressed in building codes for design against ground shaking effects. Relative risk is independent of fault activity rate, but does depend on regional constants, principally those describing the attenuation of MM intensities. For a site over an isolated fault in the Wellington, New Zealand region the risk of damage from fault rupture appears to be about equal to that from ground shaking for buildings with poor earthquake resistance (e.g. unreinforced masonry structures). But for structures designed to have some resistance to ground shaking, the risk due to fault rupture is considerably greater than that due to ground shaking. 相似文献
15.
Use of GRACE determined secular gravity rates for glacial isostatic adjustment studies in North-America 总被引：3，自引：1，他引：2
Monthly geopotential spherical harmonic coefficients from the GRACE satellite mission are used to determine their usefulness and limitations for studying glacial isostatic adjustment (GIA) in North-America. Secular gravity rates are estimated by unweighted least-squares estimation using release 4 coefficients from August 2002 to August 2007 provided by the Center for Space Research (CSR), University of Texas. Smoothing is required to suppress short wavelength noise, in addition to filtering to diminish geographically correlated errors, as shown in previous studies. Optimal cut-off degrees and orders are determined for the destriping filter to maximize the signal to noise ratio. The halfwidth of the Gaussian filter is shown to significantly affect the sensitivity of the GRACE data (with respect to upper mantle viscosity and ice loading history). Therefore, the halfwidth should be selected based on the desired sensitivity.It is shown that increase in water storage in an area south west of Hudson Bay, from the summer of 2003 to the summer of 2006, contributes up to half of the maximum estimated gravity rate. Hydrology models differ in the predictions of the secular change in water storage, therefore even 4-year trend estimates are influenced by the uncertainty in water storage changes. Land ice melting in Greenland and Alaska has a non-negligible contribution, up to one-fourth of the maximum gravity rate.The estimated secular gravity rate shows two distinct peaks that can possibly be due to two domes in the former Pleistocene ice cover: west and south east of Hudson Bay. With a limited number of models, a better fit is obtained with models that use the ICE-3G model compared to the ICE-5G model. However, the uncertainty in interannual variations in hydrology models is too large to constrain the ice loading history with the current data span. For future work in which GRACE will be used to constrain ice loading history and the Earth's radial viscosity profile, it is important to include realistic uncertainty estimates for hydrology models and land ice melting in addition to the effects of lateral heterogeneity. 相似文献
16.
Data use and information creation: challenges for marine scientists and for managers 总被引：1，自引：0，他引：1
In the coastal waters of European countries and in the offshore waters of the north-east Atlantic, there is an increasing need for scientists to meet challenging objectives, such as to identify meaningful measures of 'quality', and to recommend 'indicators' to underpin implementation of directives, conventions, statutes and other more informal national and international initiatives. Those indicators may relate to particular species or habitats, to changes in physical and chemical characteristics, and even to the use to which the system is put. The problems to be overcome are difficult, but new and developing approaches will make a significant contribution. The approaches include: criteria to identify 'sensitivity' and 'importance', structures to organise information and electronic information resources to access data.The real challenge is to make the results of the various scientific initiatives relevant to and understandable by a wide range of customers with similar overlapping requirements, and thus make a genuine contribution to protecting the marine environment. Above and beyond that is the need for scientists to drive the agenda to enable real and lasting progress to be made towards ecosystem-based management of our seas and a proper consideration of what 'sustainability' may mean in the marine environment and how we utilise its resources. 相似文献
17.
Ingo Haag 《洁净——土壤、空气、水》2006,34(6):549-559
In this paper the Basic Water Quality Model (BWQM) for the central part of River Neckar is used to analyse the oxygen budget and to assess the potentials of various measures to prevent or mitigate critical dissolved oxygen (DO) declines. It is shown that the oxygen budget is mainly governed by phytoplankton dynamics. The excessive growth of algae and the sudden break down of the resulting algal blooms may cause episodic DO depressions. Therefore, to stabilise the oxygen budget in a sustainable way, eutrophication has to be controlled within the central part of River Neckar and the upstream regions. The only feasible way to reach this goal appears to be a further drastic reduction of phosphorus emissions. In addition, it is indispensable to hold the very high standards of biochemical oxygen demand and ammonium retention at the wastewater treatment plants. A worse performance of the treatment plants would dramatically aggravate critical DO declines which may be caused by algae dynamics. As long as the oxygen budget is not completely stabilised, weir and turbine aeration can be used to mitigate DO depressions. It could be shown that the potentials of these measures suffice to keep DO at a tolerable level. However, due to the long travel times in River Neckar, it is important to start aeration up to several days before the DO minimum is reached. 相似文献
18.
The advent of missions comprised of phased arrays of spacecraft, with separation distances ranging down to at least mesoscales, provides the scientific community with an opportunity to accurately analyse the spatial and temporal dependencies of structures in space plasmas. Exploitation of the multi-point data sets, giving vastly more information than in previous missions, thereby allows unique study of their small-scale physics. It remains an outstanding problem, however, to understand in what way comparative information across spacecraft is best built into any analysis of the combined data. Different investigations appear to demand different methods of data co-ordination. Of the various multi-spacecraft data analysis techniques developed to affect this exploitation, the discontinuity analyser has been designed to investigate the macroscopic properties (topology and motion) of boundaries, revealed by multi-spacecraft magnetometer data, where the possibility of at least mesoscale structure is considered. It has been found that the analysis of planar structures is more straightforward than the analysis of non-planar boundaries, where the effects of topology and motion become interwoven in the data, and we argue here that it becomes necessary to customise the analysis for non-planar events to the type of structure at hand. One issue central to the discontinuity analyser, for instance, is the calculation of normal vectors to the structure. In the case of planar and ‘thin’ non-planar structures, the method of normal determination is well-defined, although subject to uncertainties arising from unwanted signatures. In the case of ‘thick’, non-planar structures, however, the method of determination becomes particularly sensitive to the type of physical sampling that is present. It is the purpose of this article to firstly review the discontinuity analyser technique and secondly, to discuss the analysis of the normals to thick non-planar structures detected in magnetometer data. 相似文献
19.
为实现从注重灾后救助向注重灾前预防转变,如何提高地震灾害监测预警和风险防范能力成为我们关注的重点.本文给出了国际上GNSS位移记录、强震动加速度记录、测震速度记录在地震预警中的应用现状,并总结了各自的特点,归纳出围绕高频GNSS地震学在震级与破裂过程实时反演中的几个需要进一步研究的关键问题：（1）引入北斗系统,基于高频GNSS（GPS/BDS）双系统的实时位移解算方法来提高实时单站位移解算精度,使实时解算精度达到厘米级;（2）开展强震仪加速度记录基线偏移校正研究,弥补地震近场GNSS站密度不足问题;（3）强震仪加速度记录与GNSS位移记录特点不同,开展强震仪加速度数据与GNSS位移数据实时融合处理研究,快速获得包含丰富地震形变和速率的波形数据;（4）测震学方法可快速估算震级,但是在强震发生时会出现震级饱和现象,造成震级估算偏低.需要开展基于GNSS位移时间序列的多种方法相结合的实时震级估算方法研究,通过与地震学方法比较和结合,来得到精度高、计算快的震级估值算法;（5）基于高频GNSS、断层初始模型快速选取、断层尺度、参数自适应调整是快速判断断层破裂方向的基础,在断层破裂过程自适应准实时反演算法方面需要进一步加强.通过国内外研究现状调研、分析,表明基于高频GNSS地震学的震级快速确定、震源破裂过程准实时反演算法的发展将对我国地震预警系统从"二网融合"到"三网融合"提供坚实的技术支撑. 相似文献